The human hip girdle (see FIGS. 1 and 2) is made up of three large bones joined by two relatively immobile joints. One of the bones is called the sacrum and it lies at the bottom of the lumbar spine, where it connects with the L5 vertebra. The other two bones are commonly called “hip bones” and are technically referred to as the right ilium and the left ilium. The sacrum connects with both hip bones at the left and right sacroiliac joints (SI-Joint).
The SI-Joint is a diarthrodial joint and operates to transfer large mechanical loads between the low back and the legs, while simultaneously allowing enough movement for the spine and extremities to function normally during daily activities. The sacral side of the SI-Joint contains hyaline cartilage that moves against fibrocartilage on the iliac side. The joint is generally L-shaped with ridges and depressions that interlock the sacrum and the ilium. This interlocking increases friction and minimizes motion allowing the joint to have a small amount of movement.
When the joint has excessive motion, normal function of SI-Joint can be disrupted and the joint may become inflamed causing pain. The SI-Joint has been described as a pain generator for up to 22% of lower back pain. To relieve pain generated from the SI-Joint and restore normal function of the SI-Joint, surgical treatment may be indicated. For example, surgical treatment may be indicated for degenerative sacroiliitis, inflammatory sacroiliitis, iatrogenic instability of the sacroiliac joint, osteitis condensans ilii, or traumatic fracture dislocation of the pelvis. Currently, problems associated with the SI-Joint are typically treated non-surgically with medications, limiting activity, undergoing a therapy and exercise program, or radiofrequency ablation. For more serious SI-Joint problems, surgery may be performed to fuse the Si-joint, eliminating motion between the sacrum and the ilium.
There is a need for improved treatments for addressing chronic hip, joint or back pain caused by the SI-Joint.